Lighting systems for room illumination are known in various embodiments. Generally these systems can comprise a large variety of light sources for different purposes. For example ambient light sources are used to provide an ambient lighting for room illumination. In some cases ambient light sources play a significant role for creating a room atmosphere. In working rooms the ambient lighting serves to illuminate the working places on an intermediate intensity level sufficient for general orientation and to provide an overview over the working space.
Additional task light sources are provided to illuminate a predetermined area and to produce a light that is directed to a working surface. The intensity of the task light sources can be varied between a low state and a maximum level. A lighting system comprising ambient light sources and additional task light sources provides a large flexibility to create different lighting situations.
This flexibility is also important in terms of reduction of energy consumption of the lighting system. To reduce the energy consumption, it is desired not to run all light sources of the lighting system at full power, especially in a system which comprises a large number of light sources. It is rather preferred to operate just as many light sources as necessary for an acceptable illumination of a working place, for example, with just as much power as necessary. However, this requirement cannot be fulfilled easily in many situations. In cases where each light source or groups of light sources are provided with switches to operate the respective light sources or groups of light sources individually, the extend of energy consumption depends on the user behavior.
For this reason different approaches have been made to operate the light sources of the lighting system automatically. One way of controlling the light sources is to provide sensors like occupancy sensors which detect the room occupancy and switch the light on or off according to the detected occupancy state. By using occupancy sensors, it is also possible to monitor different zones of one room and to operate the light sources illuminating these zones individually.
However, with increasing complexity of the lighting system, this way of controlling the lighting system reaches its limits. For economic reasons it is unacceptable to provide each light source with an individual occupancy sensor. Simplifying the system by connecting different light sources, such as the ambient light sources, by a wiring to create a network which can be controlled from one single controller leads to high installation costs because of the wiring of the light sources with each other, apart from the fact that the flexibility of the system is reduced in this case.
It is therefore the object of the present invention to create a lighting system of the above kind which can be installed with low installation costs but can be operated with decreased energy consumption, keeping the flexibility of the lighting system at a high level so that the system can automatically react to different lighting situation depending on the needs of the user. Another object is the provision of a method for controlling such a lighting system.